Imprinting method with embossing foil free to expand for nano-imprinting of recording media

ABSTRACT

An imprinting method is described. The imprinting method including clamping a portion of an embossing foil to a first die of a die press with a spring tensioned clamp, receiving a magnetic recording disk in the die press, and pressing the embossing foil against the magnetic recording disk to emboss a side of the magnetic recording disk with a discrete track recording pattern.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/614,334, filed Nov. 6, 2009, now U.S. Pat. No. 8,402,638 which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

This invention relates to the field of manufacturing, and morespecifically, to a press system for nano-imprinting of recording media.

BACKGROUND

A disk drive system typically has one or more magnetic recording media(a.k.a., disks) and control mechanisms for storing data withinapproximately circular tracks on the disk. The magnetic recording mediais composed of a substrate and one or more layers deposited on thesubstrate. A substrate may be produced from a blank sheet of, forexample, metal-based material such as aluminum or aluminum magnesium.The sheet may be punched to generate a disk-shaped substrate having aninner diameter (ID) and an outer diameter (OD). The disk-shapedsubstrate may be further processed (e.g., polished, textured, layerdeposition, etc.) to produce the magnetic recording disk.

Advancing the art of magnetic hard disk drives involves increasing therecording density of a disk drive system. Recording density is a measureof the amount of data that may be stored in a given area of disk. Onemethod for increasing recording densities is to pattern the surface ofthe disk to form discrete tracks, referred to as discrete trackrecording (DTR). The recessed zones separate the raised zones to inhibitor prevent the unintended storage of data in the raised zones.

One method of producing DTR magnetic recording media includes using apress to imprint embossable films residing on one or both sides of therecording disk substrate. The press utilizes a die for each side of themedia to be imprinted. The die may include an embossing foil, orstamper, that is pressed into the embossable film of the media to formthe imprinted pattern in the film. The pattern is subsequentlytransferred to the substrate and/or one or more layers residing abovethe substrate.

A press for magnetic recording disks may utilize a mandrel, or shaft,having a diameter that is sized to engage the ID of the disk. The dieshave a cylindrical opening sized to receive the mandrel. The embossingfoil is disposed around the mandrel and, thus, has an annular, or disk,shape with an inner diameter (i.e., a hole, or cavity, at theircenters). Alignment of the embossing foil to the recording media is veryimportant to achieve proper function in the recording media and suchalignment is very challenging, particularly for double-side recordingmedia where alignment of a mandrel holding a disk to an embossing foilon a first (bottom) die may induce alignment error relative to anotherembossing foil on a second (top) die. A press which maintains propercentering of a disk to both the top and bottom die as the press isoperated from an open to a closed position is therefore advantageous.

Throughput of presses for magnetic recording disks may also be limitedby the need to accurately imprint sub-micron (e.g., nanometer) featureswith high precision. For example, it is difficult to drive a pressrapidly from an open state, where the dies are displaced far enough fromone another that a disk may be loaded or unloaded from the press, toclosed state, where nanometer features are formed (all the whilemaintaining the centering of the disk). A press which improves the rateat which it transitions from the open to closed state is therefore alsoadvantageous.

A single-sided press for magnetic recording disks may also have anembossing foil affixed to a die. It can be challenging to prevent afoil-to-die coupling mechanism present on a first die of a double-sidedpress from adversely impacting the coupling mechanism on an opposing dieas the press is closed. Furthermore, both single and double-side presssystems are susceptible to the embossing foil bowing uncontrollably fromcenter to edge (e.g., under the foil's own weight) while the press is inan open state, or buckling while the press is in a closed state (e.g.,from radial expansion of the foil), either of which may produce awaviness in the imprinted features. A foil-to-die coupling mechanismwhich can overcome these difficulties is advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates a nano-imprinting press system in accordance with anembodiment;

FIG. 2A illustrates a cross sectional view of a single-sided die setwhich may be incorporated into the nano-imprinting press system of FIG.1, in accordance with an embodiment;

FIG. 2B illustrates a cross sectional view of a double-sided die setwhich may be incorporated into the nano-imprinting press system of FIG.1, in accordance with an embodiment;

FIG. 3A is a state diagram illustrating states of an imprintingoperation, in accordance with an embodiment;

FIG. 3B is a flow diagram illustrating a two phase pressing method, inaccordance with an embodiment;

FIG. 3C is a flow diagram illustrating a double-sided pressing method,in accordance with an embodiment;

FIG. 3D is a flow diagram illustrating a pressing method, in accordancewith an embodiment;

FIG. 4 illustrates a cross sectional view of a portion of a double-sideddie set in an open state, in accordance with an embodiment;

FIG. 5A illustrates a cross sectional view of a portion of adouble-sided die set in a first closing state, in accordance with anembodiment;

FIG. 5B illustrates an expanded cross sectional view of a portion of thedouble-sided die set depicted in FIG. 5A, in accordance with anembodiment;

FIG. 6A illustrates a cross sectional view of a portion of adouble-sided die set in a second closing state, in accordance with anembodiment;

FIG. 6B illustrates an expanded cross sectional view of a portion of thedouble-sided die set depicted in FIG. 6A, in accordance with anembodiment;

FIG. 7A illustrates a cross sectional view of a portion of adouble-sided die set transitioning from the second closing state to athird closed state, in accordance with an embodiment;

FIG. 7B illustrates an expanded cross sectional view of a portion of thedouble-sided die set depicted in FIG. 7A, in accordance with anembodiment;

FIG. 8A illustrates a cross sectional view of a portion of adouble-sided die set in a fourth closing state, in accordance with anembodiment;

FIG. 8B illustrates an expanded cross sectional view of a portion of thedouble-sided die set depicted in FIG. 8A, in accordance with anembodiment;

FIG. 9 illustrates a cross sectional view of a portion of a double-sideddie set in a closed state, in accordance with an embodiment;

FIG. 10A illustrates a cross sectional view of a portion of asingle-sided die set in closed state prior to imprinting, in accordancewith an embodiment;

FIG. 10B illustrates an expanded cross sectional view of a portion ofthe single-sided die set depicted in FIG. 10A, in accordance with anembodiment;

FIG. 11A illustrates a cross sectional view of a portion of asingle-sided die set in the closed state while imprinting, in accordancewith an embodiment;

FIG. 11B illustrates an expanded cross sectional view of a portion ofthe single-sided die set depicted in FIG. 11A, in accordance with anembodiment;

FIG. 12A illustrates an isometric view of a single-sided embossing foilholder assembly, in accordance with an embodiment;

FIG. 12B illustrates cross-sectional views of the assembly in FIG. 12A,in accordance with an embodiment;

FIG. 13A illustrates an isometric view of a double-sided embossing foilholder assembly, in accordance with an embodiment;

FIG. 13B illustrates a bottom-up plan view of a top side of the assemblydepicted in FIG. 13A, in accordance with an embodiment;

FIG. 13C illustrates a top-down plan view of a bottom side of theassembly depicted in FIG. 13A, in accordance with an embodiment;

FIG. 13D illustrates a cross sectional view of the assembly depicted inFIG. 13A, in accordance with an embodiment;

FIG. 13E illustrates an exploded isometric cross sectional view of theassembly depicted in FIG. 13A, in accordance with an embodiment;

FIG. 14A illustrates a cross sectional view of a single-sided embossingfoil holder mounted in a press system die, in accordance with anembodiment; and

FIG. 14B illustrates a cross sectional view of the single-sidedembossing foil holder of FIG. 13A when a press system is in a closedposition, in accordance with an embodiment.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as examples of specific, components, processes, etc., to provide athorough understanding of various embodiments of the present invention.It will be apparent, however, to one skilled in the art that thesespecific details need not be employed to practice various embodiments ofthe present invention. In other instances, well known components ormethods have not been described in detail to avoid unnecessarilyobscuring various embodiments of the present invention.

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one member with respect to other members. As such,for example, one member disposed over or under another member may bedirectly in contact with the other member or may have one or moreintervening members. Moreover, one member disposed between members maybe directly in contact with the two members or may have one or moreintervening members. In contrast, a first member “on” a second member isin contact with that second member. Additionally, the relative positionof one member with respect to other members is provided assumingoperations are performed relative to a substrate without considerationof the absolute orientation of the substrate. For example, the terms“top” and “bottom” are to be understood as merely convenient labelsdescribing only a relative physical relationship, and as such, “top” and“bottom” components may generally swap position while still achievingthe same technical effect.

It should be noted that the apparatus and methods discussed herein maybe used with various types of disks. In the exemplary embodiment, forexample, the apparatus and methods discusses herein are used with amagnetic recording disk. Alternatively, the apparatus and methodsdiscussed herein may be used with other types of digital recordingdisks, for example, a compact disk (CD), a digital versatile disk (DVD),and a magneto-optical disk.

FIG. 1 illustrates one embodiment of a press system 100 thatincorporates one or more of the components as further describedelsewhere herein. An upper portion of the press system 100 includes topcross beam 120, top die 102, bottom die 104, and press top base plate106. Top die 102 and bottom die 104 are coupled by posts (e.g., posts110, 111). The base portion of each post has a bushing (e.g., bushings114, 115). The top die 102 also includes a top holder mount base 242 forreceiving a top holder mount (not depicted in FIG. 1.) to which a topembossing foil 150 is held. The bottom die 104 includes a bottom holdermount base 142 for receiving a bottom holder mount (not depicted in FIG.1.) to which a bottom embossing foil (not shown in FIG. 1) is held. Inthe depicted embodiment, the bottom holder mount base 142 is disposedabove a bottom die holder base 146 and a bottom die holder base plate148. Although not depicted, the top holder mount base 242 may besimilarly assembled over a holder base plate.

A lower portion of the press system 100 includes a gas actuator 160disposed between the first press bottom base plate 107 and the secondpress bottom base plate 167. The first press bottom base plate 107 maybe rigidly mounted relative to the press top base plate 106 (e.g., onopposing sides of a table) so that a linear displacement of the secondpress bottom base plate 167 relative to the base plates 106, 107 istranslated, via the main rods 109, into a linear motion of the top die102 relative to the bottom die 104. A bottom cross beam 122 is disposedbelow the second press bottom base plate 167. Springs 162, 163, 161, and164, on spring rods 130, 131, 132, and 133, compress the gas actuator160 between the first press bottom base plate 107 and the second pressbottom base plate 167. In one embodiment, during operation of the presssystem 100, as the gas actuator 160 expands, the second press bottombase plate 167 moves downward and away from the first press bottom baseplate 107. This expansion causes the top cross beam 120 to lower anddisplace the top holder mount base 242 and the bottom holder mount base142 toward each other to be in one or more closed states.

The press system 100 may be configured for either single-sidedimprinting or double-side imprinting by adapting the top die 102 and/orbottom die 104. FIG. 2A illustrates an enlarged cross sectional view ofone embodiment of a single-sided die set which may be incorporated intothe press system 100. In FIG. 2A, the cross-sectional axis a-a′ issubstantially aligned with the top cross beam 120 of FIG. 1.

As shown in FIG. 2A, bottom holder mount base 142 is coupled to thebottom die holder base 146 in the bottom die 104. Similarly, a top dieholder mount base 242 is coupled to the top die base plate 246 in thetop die 102. A bottom embossing foil 251 is disposed above a bottompress pad 280 of the bottom die 104 and coupled by the bottom holdermount 1210 to the bottom holder mount base 142. In one embodiment, thebottom press pad 280 may include be one or more elastomeric layers thatallow for a uniform press of nanoscopic imprinting features in thebottom embossing foil 251 against an embossable film of a recordingmedia disk substrate 255. A bottom rod 284 extends through a centerportion of the bottom die 104. The bottom rod 284 is sized to engage aninner diameter (ID) of the recording media disk substrate 255. A bottomball bushing 288 surrounds the elongated portion of the bottom rod 284,and a bottom outer sleeve 290 surrounds the bottom ball bushing 288. Thebottom outer sleeve 290 and the bottom rod 284 combine to form a bottommandrel with a bottom rod spring 285 disposed between the bottom outersleeve 290 and an end of the bottom rod 284 distal from the recordingmedia disk substrate 255. The bottom outer sleeve 290 is, in turn,disposed on a bottom mandrel spring 291.

The bottom holder mount base 142 further includes a bottom standoff 243which is configured to contact the top standoff 244 when the top andbottom dies 102,104 are brought into contact when the press system is ina closed state, as further described elsewhere herein. A top rod 294extends through a center portion of the top die 102 and is coupled tothe top die 102 via a top mandrel spring 295.

FIG. 2B illustrates a cross sectional view of one embodiment of adouble-sided die set which may be incorporated into the press system ofFIG. 1 for the imprinting of both sides of a recording media. In FIG.2B, the cross-sectional axis a-a′ is substantially aligned with the topcross beam 120 of FIG. 1. As depicted in FIG. 2B, the bottom die 104includes substantially the same components as described in FIG. 2A whilethe top die 102 includes additional components facilitating a secondside of imprinting. In the exemplary embodiment depicted, the topmandrel is separated into a top outer sleeve and a top rod 294 having atop mating surface 296. The top mating surface 296 is configured to matewith a bottom mating surface 286 of the bottom rod 284, as furtherdescribed elsewhere herein. A top ball bushing 270 surrounds anelongated portion of a top rod 294 with the top outer sleeve 271surrounding the top ball bushing 270. A top rod spring 275 is disposedbetween the top outer sleeve 271 and an end of the top rod 294 distalfrom the top mating surface 296. The top outer sleeve 271 is, in turn,disposed on the top mandrel spring 295. The top rod 294 is thereforemovable relative to the top outer sleeve 271 along a longitudinalmandrel axis as a function of the top rod spring 275 while the top outersleeve 271 is also movable relative to the top die 102 as a function ofthe top mandrel spring 295. A top embossing foil 150 is disposed over atop press pad 276 of the top die 102 and coupled by the top holder mount1350 to the top holder mount base 242. In one embodiment, the press pad276 may include be one or more elastomeric layers that allow for auniform press of nanoscopic imprinting features in the top embossingfoil 150 against an embossable film of a recording media disk substrate255.

In one embodiment, the top and bottom ball bushings 270 and 288 hold thetop/bottom rods 294, 284 in precise alignment with the top/bottom outersleeves 271, 290, respectively, to center embossing foils 150, 251 witha longitudinal axis of the respective top/bottom rod. This allows for aconcentricity to be established and maintained between the embossingfoils 150,251 and the rods 294, 284. At least one of the top or bottomdies includes an opening with a larger diameter than the outer diameterof the outer sleeve to allow radial movement of a mandrel relative tothe die through which the mandrel passes as the top and bottom rods arealigned to a common longitudinal mandrel axis upon closing the press.When the top rod is aligned to the bottom rod, the concentricity of thesleeves to the rods and the concentricity of the foils to the sleevesensure that the recording media disk substrate 255 engaged by a rod isconcentric with both the top and bottom embossing foils.

As depicted in FIGS. 2A and 2B, either or both of the top and bottomdies 102, 104 may further include a chamber volume which may bepressurized to displace a piston relative to the die assembly in whichthe piston is housed. In the exemplary double-sided die set depicted inFIG. 2B, the piston 278 is disposed within the top die 102 to provide aforce against a top press pad 276 through which an imprinting force maybe applied to the top embossing foil 150, as further described elsewhereherein.

FIG. 3 is a state diagram illustrating a nano-imprinting operation 300,in accordance with one exemplary embodiment. The states depicted in thenano-imprinting operation 300 are performed during one pressing cycle(i.e., from open to closed to open). FIGS. 4-9 illustrate crosssectional views of a portion of a double-sided die set in the states ofFIG. 3. While FIG. 3 is described in the context of double-sidedimprinting, many or all of the same states described may be performedduring a single-sided imprinting operation.

Generally, in response to application of a continuous closing force,upon aligning the workpiece to one of the mandrel rods (e.g., the bottomrod 284), the nano-imprinting operation 300 maintains a positivepressure against the aligned workpiece throughout the duration of thepressing operation (e.g., throughout all closing states) to establishand preserve a centering of the workpiece relative to both the top andbottom dies 102, 104.

The nano-imprinting operation 300 begins at the open state 301 withfirst receiving a workpiece into a press system. As illustrated in FIG.4, when in an open state with the opposing dies spaced apart from oneanother, the bottom rod spring 285 is in a relatively decompressed statewhich extends the bottom rod 284 above the bottom outer sleeve 290 toreceive the recording media disk substrate 255. The bottom outer sleeve290 is similarly displaced outward relative to the bottom holder mountbase 142 by the compressive force of the bottom mandrel spring 291. Thebottom outer sleeve 290 includes a notch 230 which engages a cam (notdepicted) to position the bottom outer sleeve 290 relative to the bottomholder mount base 142. This outward extension of the bottom outer sleeve290 is set by the cam's position relative to the notch 230 to form abottom doming 228 in the bottom embossing foil 251. Lifting the bottomouter sleeve 290 creates a dome-like shape (bottom doming 228) along aninner radial distance, or center, of the bottom embossing foil 251. Thedome in the center portion of the bottom embossing foil 251 assists inseparating the recording media disk substrate 255 from the surface ofbottom embossing foil 251 when the press returns from a closed state tothe open state after completing an imprinting process.

Similarly, when in an open state, the top rod spring 275 is in arelatively decompressed state. The top rod 294 is displaced beyond thetop outer sleeve 271 and the top holder mount base 242, in preparationfor receiving the bottom rod 284. The top outer sleeve 271 extendsoutward from the top holder mount base 242 in response to thecompressive force of the top mandrel spring 295. The top outer sleeve271 also includes a notch 231 which engages a cam (not depicted) toposition the top outer sleeve 271 relative to the top holder mount base242. This outward extension of the top outer sleeve 271 is set by thecam's position relative to the notch 231 to form a top doming 233 in thetop embossing foil 150. In addition to defining the ready positions ofthe upper and lower rods and outer sleeves, the cams in the top andbottom dies 102, 104 may also set a controllable amount of springpre-load in the mandrel springs 291, 295. Cam-notch arrangements mayalso be employed to set a controllable amount of spring pre-load intoeither or both of the top and bottom rod springs 275, 285. In oneembodiment, when the press is in the open state, the four opposingsprings (top and bottom rod springs 275, 285 and top and bottom mandrelsprings 291, 295) are preloaded asymmetrically. As one example, thebottom rod spring 285 is preloaded to a force of 2.1 lbs, the bottommandrel spring 291 is preloaded to 9.3 lbs, the top rod spring 275 ispreloaded to 1.7 lbs, and the top mandrel spring 295 is preloaded to12.5 lbs.

As further illustrated in FIG. 4, the recording media disk substrate 255is disposed onto a male conical surface 287 configured to have a rangeof outer diameters (OD) inclusive of the inner diameter (ID) of therecording media disk substrate 255 to hold the substrate 255 (e.g., bygravity). During the open state depicted in FIG. 4, the orientation ofsubstrate 255 may be non-orthogonal to the top mandrel longitudinal axis223 or bottom mandrel longitudinal axis 224. For example, the recordingmedia disk substrate 255 may be centered about the bottom mandrellongitudinal axis 224 but still have a radial axis non-orthogonal to thebottom mandrel longitudinal axis 224. Furthermore, while in the openstate, the top mandrel longitudinal axis 223 may also be misalignedrelative to the bottom mandrel longitudinal axis 224.

With the press system 100 loaded, a closing force is applied (e.g., viathe gas actuator 160) which linearly displaces the top and bottom dies102, 104 toward each other. The components of the press system 100 thenundergo a sequence of configurations, referred to herein as “closingstates” in response to the displacement of the top and bottom dies 102,104. The physical characteristics of particular closing states aredependent upon the relative dimensions, positions and forcerelationships between the components of the top and bottom dies 102,104.

Returning to FIG. 3, at the closing state 305, a first mandrel rod ismated with the opposing second mandrel rod and, one of the mandrelsleeves is allowed to move within a clearance in the die which alignsthe longitudinal axis of each of the first and second rods along a samelongitudinal mandrel axis as the press continues to close. In theembodiment depicted in FIG. 5A, as the press is closed, the top rod 294touches the bottom rod 284 with the top mating surface 296 makingcontact with the bottom mating surface 286. FIG. 5B illustrates anexpanded cross sectional view of a portion of a double-sided die set inthe closing state 305, in accordance with an embodiment. In theexemplary embodiment, at least one of the bottom and top rods 284, 294include a female conical or tapered end surface which couples to a maleend surface of the other rod to generate a radial alignment forcebetween the mating rod surfaces as the press continues to close andsprings 275, 285, 291 and 295 apply a force along the longitudinalmandrel axis opposing the closing force. In the exemplary embodiment,the bottom mating surface 286 forms a female conical surface spanning arange of inner diameters (ID) inclusive of the outer diameter (OD) ofthe non-conical top mating surface 296.

Following initial contact of the opposing mandrel rods, as the dies aredisplaced toward one another (e.g., in direction substantially parallelto the longitudinal mandrel axis 229), the conical shape of the bottommating surface 286 displaces either or both of the bottom and top rods284, 294 in a radial direction (orthogonal to the longitudinal mandrelaxis) within the die clearance to align the top mandrel longitudinalaxis 223 with the bottom mandrel longitudinal axis 224 and form thecommon longitudinal mandrel axis 229. In alternative embodiments, a maleconical mating surface, such as that depicted in FIG. 2A may couple to afemale non-conical mating surface to align the top and bottom mandrelrods. Because the ball bushings 288 and 277 expand radially to hold afirm contact with outer sleeves 271 and 290, closing state 305 centersthe alignment of the embossing foils 150, 251 about the commonlongitudinal mandrel axis 229.

As further shown in the expanded view of FIG. 5B, the bottom outersleeve 290 is further coupled to a bottom shoulder ring 292. While thebottom shoulder ring 292 may be a collar machined into a portion of thebottom outer sleeve 290, in the exemplary embodiment depicted, thebottom shoulder ring 292 is a separate component such that the bottomouter sleeve 290 becomes an assembly. An outer diameter of the bottomshoulder ring 292 is substantially equal to an inner diameter of thebottom embossing foil 251. In the exemplary embodiment, the bottomembossing foil 251, annular in shape, has an inner circumferentialsurface directly bonded to the bottom shoulder ring 292. The bottomshoulder ring 292 centers the bottom embossing foil 251 to alongitudinal axis of the bottom outer sleeve 290 (which is aligned withthe longitudinal mandrel axis 229). The bottom outer sleeve furtherincludes a radial support surface 226 extending radially from the bottomshoulder ring 292 to an outer diameter larger than the inner diameter ofthe bottom embossing foil 251. The radial support surface 226 isconfigured to be in direct contact with a back surface of an innerradial portion of the bottom embossing foil 251. In the exemplaryembodiment, radial support surface 226 is directly bonded to a portionof the back surface of the bottom embossing foil 251. As further shownin FIG. 5B, the bottom shoulder ring 292 extends along the longitudinalmandrel axis 229 beyond the radial support surface 226 by an amount, H.In the exemplary embodiment, the distance H is less than the thicknessof the bottom embossing foil 251.

In FIG. 5B, the top outer sleeve 271 is coupled to a top shoulder ring272 to form a top sleeve assembly similar to the bottom sleeve assembly.The top outer sleeve 271 centers the top embossing foil 150 to alongitudinal axis of the top outer sleeve 271 (which is aligned with thelongitudinal mandrel axis 229). The top outer sleeve 271 furtherincludes a radial support surface 227 extending radially from the topshoulder ring 272 to an outer diameter larger than the inner diameter ofthe top embossing foil 150. The radial support surface 227 is in directcontact with a back surface of an inner portion of the top embossingfoil 150 and, in the exemplary embodiment, is directly bonded to theback surface of the top embossing foil 150. Similar to the bottomshoulder ring 292, the top shoulder ring 272 extends along thelongitudinal mandrel axis 229 beyond the radial support surface 227,preferably by an amount less than a thickness of the top embossing foil150.

For embodiments where the top or bottom shoulder ring 272, 292 formspart of a bottom sleeve assembly (e.g., as depicted in FIG. 5B), theshoulder rings 272, 292 may be of a material different than that of theradial support surfaces 226, 227. In one advantageous embodiment, theshoulder ring(s) is of a first material having a different coefficientof thermal expansion than the material of the radial support surface(s),thereby enabling the shoulder ring to be assembled into the outersleeve(s) at a first temperature and affixed upon reaching a secondtemperature, different than the first temperature (e.g., press systemoperating temperature). As one example, the bottom shoulder ring 292 isan aluminum ring pressure fit to an inner circumference of the bottomouter sleeve 290. After the pressure fitting, the bottom shoulder ring292 and the radial support surface may then be machined at the same timeto form a contiguous machined surface. For such an exemplary embodiment,the top shoulder ring 272 may similarly form a contiguous machinedsurface with the radial support surface 227.

Returning to FIG. 3, with the top and bottom rods 284, 294 aligned, thenano-imprinting operation 300 proceeds to the closing state 310. Aspreviously noted, the opposing rod springs and mandrel springs havedifferent spring strengths which serve to asymmetrically displace thefirst and second mandrels from an open state to various sequentialclosed states in response to a closing force of the press whichdisplaces the top and bottom dies 102, 104 toward each other. As thepress continues to close, at the closing state 310, a first rod springis compressed before a second rod spring compresses so that a firstouter sleeve applies pressure to the workpiece against the rod carryingthe workpiece. The shape of the first outer sleeve (e.g. height of ashoulder ring) is such that the first outer sleeve causes a domed innerportion (ID) of a first embossing foil to directly contact the workpieceand level the workpiece to be orthogonal to the common mandrel axis.

In the exemplary embodiment depicted in FIG. 6A, the bottom rod spring285 applies a larger spring force than the top rod spring 275 such thatthe top rod spring 275 compresses before the bottom rod spring 285. Withthe top rod spring 275 compressing at a lower press closing force thanthe bottom rod spring 285, the top rod 294 retracts in response to thepress closing force until the top outer sleeve 271 begins to apply anopposing force against the recording media disk substrate 255.

FIG. 6B illustrates an expanded cross sectional view of a portion of adouble-sided die set in the closing state 310. With the bottom rodspring 285 not yet fully compressed, a gap, G, remains between therecording media disk substrate 255 and the bottom embossing foil 251.Because the top shoulder ring 272 has a height slightly less than thethickness of the top embossing foil 150, the force provided by the topouter sleeve 271 is applied to the recording media disk substrate 255through the portion of the top embossing foil 150 that is bonded to theupper radial support surface 227. The inner circumference of the topembossing foil 150 contacts the recording media disk substrate 255 alonga radial length determined by an amount of top doming 233 present in thetop embossing foil 150. The opposing force applied by the top outersleeve 271 against the recording media disk substrate 255 serves toorient and level a radial axis of the substrate 255. In one embodiment,the opposing force applied by the top outer sleeve 271 against therecording media disk substrate 255 orients a longitudinal axis of thesubstrate 255 to be substantially parallel with the longitudinal mandrelaxis 229.

The opposing force applied by the top outer sleeve 271 while in theclosing state 310 is a function of the relative spring strengths of thetop mandrel spring 295, the bottom mandrel spring 291, the top rodspring 275 and the bottom rod spring 285. While it is the relativerelationship of spring strengths which enables the advantageousasymmetrical closing of the press system described herein, when theexemplary embodiment reaches the closing state 310, the top rod spring275 provides a force of approximately 1.9 lbs, while the bottom rodspring 285 provides a force of approximately 2.1 lbs. As such, thebottom rod spring 285 remains in the preloaded state while the top rodspring 275 is in a retracted state when the magnetic recording mediadisk substrate 255 first contacts the top embossing foil 150.

Returning to FIG. 3, with the upper and lower mandrels and workpiecealigned to a common longitudinal mandrel axis, the nano-imprintingoperation 300 proceeds to the closing state 315 in response to the pressclosing force. At the closing state 315, the second rod spring iscompressed to displace the rod carrying the substrate relative to asecond outer sleeve to eliminate the gap between the workpiece and thesecond outer sleeve. In one embodiment, at the closing state 315, aninner portion of the second embossing foil directly contacts theworkpiece. However, in alternate embodiments, the second outer sleevemay directly contact the workpiece or apply a pressure against theworkpiece through another intervening member.

In the exemplary embodiment depicted in FIG. 7A, the top and bottomouter sleeves 271, 290 are abutting with the top and bottom rods 284 and294 in a fully retracted position. Upon the exemplary press systemreaching the closing state 315, as illustrated in FIGS. 7A and 7B, thetop rod spring 275 provides a force of approximately 1.9 lbs, while thebottom rod spring 285 provides a force of approximately 3.1 lbs. Assuch, the force in the bottom rod spring 285 increases from thepreloaded state. As further illustrated in the expanded cross-sectionalview of FIG. 7B, an inner portion of both the top embossing foil 150 andthe bottom embossing foil 251 is in contact with the recording mediadisk substrate 255 with both the top and bottom doming 233, 228 stillremaining (albeit bottom doming 228 is greatly reduced) such that thetop and bottom press pads 276, 280 are not in yet in complete contactwith the embossing foils 150, 251 while the press system is in theclosing state 315.

Returning to FIG. 3, the nano-imprinting operation 300 proceeds to theclosing state 320 in response to the press closing force. To reach theclosing state 320, the second outer sleeve applies a force against theworkpiece which opposes the force applied by the first outer sleeve andthe weaker of the mandrel springs becomes the third spring to compress.A first outer sleeve is displaced until the doming in a first of theembossing foils is removed, flattening the first embossing foil coupledto the first outer sleeve. Sequentially removing the doming based onrelative mandrel spring strengths may be advantageously morecontrollable than removing both the top and bottom doming concurrently.FIGS. 8A and 8B illustrate cross sectional views of a portion of adouble-sided die set in the closing state 320, in accordance with anembodiment. The bottom doming 288 is eliminated such that the bottomembossing foil 251 is in complete contact with the bottom press pad 280while the top doming 233 remains. Upon the exemplary press systemtransitioning to the closing state 320, the top rod spring 275 forceremains at approximately 1.9 lbs (retracted top rod state), while thebottom rod spring 285 force remains at approximately 3.1 lbs (retractedbottom rod state). The top mandrel spring 295 force increases from theopen state preload force of 12.5 lbs to approximately 13.5 lbs while thebottom mandrel spring 291 increases from the open state preload force of9.3 lbs to a force of approximately 10.8 lbs.

As the press continues to apply a closing force, the nano-imprintingoperation 300 advances to the closed state 325 (FIG. 3) and the secondmandrel spring (i.e., fourth spring) is compressed to displace thesecond outer sleeve relative to the second die reducing the doming at acenter portion of the second embossing foil coupled to the second outersleeve. FIG. 9 illustrates a cross sectional view of a portion of adouble-sided die set in the closed state 325, in accordance with anembodiment. As shown, top doming 233 is reduced while the bottomembossing foil 251 is flat (i.e., bottom doming 288 is removed) whilethe top and bottom sleeves 271 and 290 are abutted against inner radiusof the recording media disk substrate 255.

Depending on the configuration of the press system, imprinting may ormay not occur upon advancing to the closed state 325 as a function ofwhether or not all of the doming in both embossing foils is eliminatedupon reaching the closed state 325. For example, in one single stepimprinting embodiment, imprinting of the workpiece occurs at the closingstates 320 and 325 as the second embossing foil is flattened. For suchembodiments, the force closing the press is the force that will imprintthe workpiece and the nano-imprinting operation 300 advances along thedotted line in FIG. 3 to the open state 301. In the exemplary embodimenthowever, no imprinting occurs until the nano-imprinting operation 300advances past the closed state 325 upon reaching a stopper which haltsmovement of the top and bottom dies 102, 104. For such embodiments,pressing is separated into two distinct phases; a “closing” phase wheremacroscopic displacement of the die sets occurs and a “closed” phasewhere microscopic displacement of the embossing foil occurs. Forexample, as further depicted in FIG. 3B, a two phase pressing method 340begins at operation 341 with a magnetic recording disk received on afirst die of a die set while the die set is in an open state (e.g., theopen state 301). Next at operation 342, the die set is closed in thefirst phase where a first embossing foil is in contact with theworkpiece and a second embossing foil is spaced apart from the magneticrecording disk by the doming in the second foil (e.g., the closed state325). At operation 343, in the second phase, a piston disposed within adie is displaced while the die set is closed (e.g., the closed state330) to reduce the doming remaining in the second embossing foil. Oncethe dome and associated gap is eliminated, the piston presses theembossing foil against the recording disk at operation 344.

The stopper can be set to prevent macroscopic displacement of theclosing dies from imprinting the recording media disk substrate 255. Thestopper defines a predetermined gap associated with the desired amountof doming to retain in the second embossing foil when the die press isclosed. The stopper enables precise control in the reduction of thedoming in the second embossing foil without over-compressing theworkpiece (e.g., compressing the press pad 280). In such embodiments,the force imprinting the workpiece is distinct from the force closingthe press. The stopper also permits the relatively large diedisplacement required between an open state suitable for loading andunloading a workpiece to be rapidly traversed in a first “closing” phaseof the nano-imprinting operation 300. A second “closed” phase of thenano-imprinting operation 300 allows for sub-micron precision with arelatively slower traversal of a distance that is at least an order ofmagnitude smaller than for the closing phase. Notably, separating thenano-imprinting operation 300 into these two phases may be practicedeven where the particular closing states 305-325 are not employed. Forexample, even for press systems which do not employ the exemplaryasymmetrical arrangement of springs depicted in FIGS. 2A-9, a stoppermay still be used as described herein.

Depending on the embodiment, the stopper may be one or more of amechanical hard stop or a die displacement controller reactive to anoptical sensor, electrical sensor, or a mechanical sensor. For amechanical hardstop, many variations are possible. For example, opposingstandoffs may be machined into the top and bottom dies 102, 104 to be insubstantial alignment with each other and proximate to an outer edge ofthe magnetic recording disk when the die set in a closed position. FIG.10A illustrates a cross sectional view of a portion of a single-sideddie set in the closed state 325 where the bottom standoff 243 makescontact with the top standoff 244. In the depicted embodiment, thestandoffs 243 and 244 make contact and serve as a mechanical stopper tohalt the displacement of the top and bottom dies 102, 104 while theembossing foil 251 is still spaced apart from a magnetic recording mediadisk substrate 255 by a predetermined gap. FIG. 10B provides an expandedcross sectional view further illustrating that the piston 278, untilsubsequently actuated, is uniformly spaced apart from the recordingmedia disk substrate 255. A non-zero gap is also present between theembossing foil 251 and the recording media disk substrate 255.

Returning to FIG. 3A, an imprinting piston is actuated to advance thenano-imprinting operation 300 from the closed state 325 to the closedstate 330. As previously described either or both dies may include oneor more imprinting pistons which may be moved relative to the first andsecond die halted by the stopper to press an embossing foil against theworkpiece. The imprinting piston(s) may be activated by pressurizing avolume chamber with a gas or liquid after the die set is stopped in theclosed position. Generally, the volume chamber is to be pressurized witha force less than a force holding the die set in the closed position.

FIG. 11A illustrates a cross sectional view of a portion of adouble-sided die set in the closed state 330, in accordance with anembodiment. In the depicted embodiment, the top piston 278 in the topdie 102 is moved toward the bottom die 104. FIG. 11B illustrates anexpanded cross sectional view of the single-sided die set depicted inFIG. 11A. As shown, the piston 278 traverses the distance, P, to pressthe embossing foil 251 against the magnetic recording media disksubstrate 255 to imprint features onto the substrate 255. For singlepiston embodiments, the distance P is at least equal to the doming whichremains after the die set is closed (e.g., between approximately 0.1 mmand 0.3 mm).

In alternate embodiments, the distance, P, may vary as dependent onfactors such as whether opposing pistons are employed and whetherimprinting pads are employed. For example, in a particular double-sidepress system, an imprinting piston is disposed in both the top andbottom dies 102, 104 such that a first volume is pressurized on a sideof a first piston opposite a first side of the workpiece and a secondvolume is pressurized on a side of a second piston opposite a secondside of the workpiece to displace the first and second pistons inopposing directions toward respective embossing foils. Each of thepistons may travel a distance, P, which is at least equal to an amountof doming between the embossing foil and the workpiece which remainsafter the die set is closed (e.g., between approximately 0.1 mm and 0.3mm).

After imprinting the workpiece, the nano-imprinting operation 300advances from the closed state 330 back to the open state 301, asdepicted in FIG. 3. The imprinting pistons (if employed) may be returnedto the recessed home position and the closing force removed or reversedto separate the die set. In the exemplary embodiment, the statesdepicted in FIG. 3 are sequentially reversed as the press closing forceprovided by the gas actuator 160 is removed. Reversal of the states inthe press operation 300 enables a controlled separation of the embossingfoils from the workpiece in a manner which maintains good fidelity ofthe imprinted features. Return springs in addition to the mandrel androd springs may be employed or other driving forces may be employed toadvance from the closed state 330 to the open state 301. Upon openingthe press system, the imprinted workpiece may be unloaded.

FIG. 12A illustrates an isometric view of an assembly 1200 whichincludes a single-sided embossing foil holder 1201 and the holder mount1210, in accordance with an embodiment. The assembly 1200 may beemployed to affix an embossing foil to a die in a nano-imprinting presssystem, such as the exemplary press system 100. FIG. 10 B, for example,illustrates the assembly 1200 mounted to the bottom die 104. The holdermount 1210 is rigidly affixed to the bottom die 104, the foil holder1201 is affixed to the holder mount 1210, and the bottom embossing foil251 is clamped between the foil holder 1201 and a portion of the bottomdie 104 (e.g., the bottom press pad 280). As shown, to allow applicationof pressure to the entire recording media disk substrate 255, thethickness of the foil holder 1201 should be no greater than thethickness of the recording media disk substrate 255.

As depicted in FIG. 12A, the foil holder 1201 is annular in shape tosurround a longitudinal mandrel axis 229 when mounted into a presssystem. The foil holder 1201 has an inner diameter 1202 which is smallerthan the outer diameter of the embossing foil 251 that is to be retainedby the assembly 1200. The foil holder 1201 is affixed to the holdermount 1210 at a radial distance beyond an outer diameter of theembossing foil 251 such that the foil holder 1201 forms a flangeoverlapping an outer circumference of the bottom embossing foil 251. Inthe depicted embodiment, the foil holder 1201 is affixed to the holdermount 1210 with a plurality of screws 1205 which pass through openings1206. As further illustrated in FIG. 12A, the openings 1207 may besimilarly utilized to affix the holder mount 1210 to a die.

FIG. 12B illustrates views of the assembly 1200 along the b-b′cross-section. As depicted, the holder mount 1210 is annularly shapedsuch that the b-b′ cross section forms two cross-sectional faces, one ofwhich is illustrated in an expanded view. The holder mount 1210 has aninner circumferential surface 1211 defining an inner diameter 1212 ofthe holder mount 1210. In an advantageous embodiment, the inner diameterof the holder mount is larger than the outer diameter of the embossingfoil 251 such that a gap, G, is formed between the outer circumferenceof the embossing foil 251 and the inner circumference of the holdermount 1210. In an exemplary embodiment, the gap G is approximately 0.1mm so that, of the components in the assembly 1200, only the foil holder1201 contacts the embossing foil 251. The foil holder 1201 pressesagainst an outer surface of the embossing foil to apply a clamping forcetoward a holder mount base (e.g., disposed in the bottom die 104 asdepicted in FIG. 10B).

FIG. 13A illustrates an isometric view of an assembly 1300 whichincludes a bottom holder mount 1310 and a top holder mount 1350 whichmay be employed to couple two embossing foils to a die set in adouble-sided press system, such as the exemplary press system 100. FIGS.13B and 13C illustrate plan views of the double-sided embossing foilholder of FIG. 13A. FIG. 13B illustrates a “bottom-up” plan view of anoverlying top holder mount (i.e., looking up from a workpiece to bepressed) while FIG. 13C illustrates a “top-down” plan view of anunderlying bottom holder mount (i.e., looking down from a workpiece tobe pressed).

As illustrated in FIG. 13B, a top foil holder 1301 includes a pluralityof holder tabs 1302 extending radially inward from the top holder mount1350 to reach an inner diameter 1303 which is smaller than the outerdiameter 151 of the top embossing foil 150. In other words, the holdertabs 1302 overlap a portion of the top embossing foil 150. For thedepicted embodiment, the inner diameter of the top holder mount 1350 islarger than the outer diameter 151 of the top embossing foil 150 (e.g.,by approximately 0.1 mm). As such, the holder tabs 1302 form first arcsegments along the circumference of the top foil holder 1301 to clampfirst portions of an outer circumference of the top embossing foil 150against an underlying surface of the top die 102 when the top holdermount 1350 is affixed to a holder mount base (e.g., holder mount base242 illustrated in FIG. 2B).

The exemplary bottom foil holder embodiment depicted in FIG. 13Cincludes a plurality of holder tabs 1325 extending radially inward fromthe bottom holder mount 1310 to reach an inner diameter 1327 which issmaller than the outer diameter 252 of the bottom embossing foil 251. Inother words, the holder tabs 1325 overlap a portion of the bottomembossing foil 251. For the depicted embodiment, the inner diameter ofthe bottom holder mount 1310 is larger than the outer diameter 252 ofthe bottom embossing foil 251 (e.g., by approximately 0.1 mm). Theholder tabs 1325 form second arc segments along the circumference of thebottom holder mount 1310 to clamp second portions of an outer perimeterof the bottom embossing foil 251 against a surface of the bottom die 104when the bottom holder mount 1310 is affixed to the bottom die 104.

As further illustrated in FIGS. 13B and 13C, the top foil holder 1301has an annular shape and a radial width which varies with angularposition about the longitudinal mandrel axis 229 while the bottom foilholder is comprised of the holder tabs 1325 which are physicallyindependent of each other and each separately affixed to the bottomholder mount 1310. In an embodiment, the holder tabs 1325 are disposedthe bottom holder mount 1310 at angular positions corresponding to wherethe first embossing foil holder, as affixed to the top holder mount1350, has the smallest radial width. To provide approximately equalclamping force to the embossing foils, the combined arc segment lengthof the holder tabs 1302 is preferably approximately equal to thecombined arc segment length of the holder tabs 1325. While the number oftabs for the top and bottom foil holders may vary while still achievingapproximately equal arc segment lengths, the number should besufficiently great to adequately distribute the foil clamping forcealong the outer circumference of the foils. In the depicted exemplaryembodiment, the number of holder tabs 1302 is equal to the number ofholder tabs 1325, with each of the holder tabs 1302, 1325 having acenter 1304 at an angular position about the longitudinal mandrel axis229 which is separated by an angle θ₁ approximately equal to 120 degreeswith the holder tabs 1302 having centers offset by approximately 60degrees from the centers of the holder tabs 1325.

FIG. 13E illustrates an exploded isometric cross-sectional view of theassembly depicted in FIGS. 13A, 13B and 1C, in accordance with anembodiment. As shown, a longitudinal thickness, T₁, of each of theplurality of holder tabs 1302 is approximately equal to the longitudinalthickness, T₂, of the each of the plurality of holder tabs 1325.Preferably, the longitudinal thicknesses T₁ and T₂ are less than alongitudinal thickness T₃ of the magnetic recording media disk substrate255. With the thicknesses T₁ and T₂ approximately equal and less thanthe thickness T₃, when a die set closed around a magnetic recordingmedia disk substrate 255 during a pressing operation the top and bottomfoil holders interdigitate to form an annulus of an approximatelyconstant thickness. Such an arrangement distributes pressing forcesuniformly along the outer perimeters of the embossing foils withoutdistorting the embossing foils. As shown in the cross-section depictedin FIG. 13D, the thicknesses and geometries described herein presentsubstantially flush surfaces to the recording media disk substrate 255for good imprinting performance.

FIGS. 13A, 13C and 13E further illustrate a support member 1375configured to be disposed around an outer perimeter of a magneticrecording disk and between the top and bottom embossing foils 150, 251when a die set is closed. The support member 1375 may serve as a spacerto prevent a detrimental collapse of the embossing foils adjacent to theouter perimeter of the magnetic recording disk. As illustrated in FIG.13E, the support member 1375 is affixed to the bottom holder mount 1310with edges adjacent to the edges of the holder tabs 1325. In oneembodiment, the support member 1375 has a thickness, T₄, greater thanthe thickness T₂ of the holder tabs 1325. In an alternative embodiment,the two components are unified into a monolithic piece which serves bothfoil holding functions and foil spacing functions.

As further shown in FIG. 13E, with the holder tabs 1302 and 1325interdigitated or interleaved, the edge 1304 is spaced apart from, butadjacent to, the edge 1327. Because the first and second arc segmentsformed by the holder tabs 1302 and 1325 are complementary, the holdertabs 1302 interdigitate with the holder tabs 1325 when the top andbottom dies 102, 104 are brought together (e.g., the exploded view ofFIG. 13D is collapsed). While conventional double-sided imprintingprocesses or conventional double-sided press systems may also takebenefit from the interdigitated tabbed foil holders described herein, ina particular embodiment, the assembly 1300 is affixed to the presssystem 100 to perform a double-sided pressing method 350, as depicted inFIG. 3C.

The method 350 begins with an outer circumference of a first embossingfoil clamped to a first die with a plurality of first tabs at operation351. For example, the top embossing foil 150 may be clamped to the topdie 102 with the holder tabs 1302. At operation 352, an outercircumference of a second embossing foil is clamped to a first die witha plurality of second tabs. For example, the bottom embossing foil 251may be clamped to the bottom die 104 with the holder tabs 1325. Next, atoperation 355, a magnetic recording disk is received into the presssystem at operation 355 (e.g., the magnetic recording media disksubstrate 255 is received into the press system 100). At operation 360,the press is closed around the magnetic recording disk by interleavingthe plurality of first tabs with the plurality of second tabs. Forexample, as the closing state 325 (FIG. 3A) is reached, the holder tabs1325 interdigitate with the holder tabs 1302 as depicted in FIG. 13D. Atoperation 365, the recording media disk is then pressed to imprint botha front side and a back side. For example, the piston 278 may beactuated during the closed state 330 as a second phase of the pressingmethod 350.

In particular embodiments, the embossing foil employed by a press systemis coupled to a die in a manner which allows the embossing foil toexpand radially during an imprinting process. Allowing such radialexpansion can reduce buckling of the embossing foil and reduce wavinessin the features imprinted into a recording media disk. In oneembodiment, an embossing foil holder, such as any of those described inthe context of assemblies 1200 and 1300, is coupled to a die whichclamps a first portion of the embossing foil in a manner which stillallows the clamped foil portion to move in a radial direction relativeto the embossing foil holder.

FIG. 14A illustrates a cross-sectional view of the single-sidedembossing foil holder 1201 mounted in a press system die, in accordancewith an embodiment. In the exemplary embodiment depicted, the presssystem is in an open state with the bottom rod 284 holding a recordingmedia disk substrate 255 and the bottom outer sleeve 290 extended awayfrom the bottom press pad 280 to form the doming 288. As describedelsewhere herein, at least a portion of an inner circumference of theembossing foil is rigidly affixed and concentric to the bottom outersleeve 290 to prohibit radial movement of the embossing foil relative tothe bottom outer sleeve 290. As illustrated in FIG. 12A, the embossingfoil holder 1201 is rigidly affixed to the holder mount 1210 with theholder mount 1210 sized to have an inner diameter larger than the outerdiameter of the bottom embossing foil 251. The effect of such a sizingis annotated in FIG. 14A as the gap, G₁, between the outer edge of thebottom embossing foil 251 and the inner edge of the holder mount 1210.As shown in FIG. 14A, with the holder mount 1210 disposed within thebottom die 104, the inner surface of the holder mount 1210 becomes asidewall of the bottom die 104 adjacent to the bottom embossing foil251. The gap G₁ between the sidewall of the bottom die 104 and thebottom embossing foil 251 provides room for the bottom embossing foil251 to move or slide radially towards the holder mount 1210. For anexemplary embodiment where the outer diameter of the bottom embossingfoil 251 is at least 0.1 mm smaller than an inner diameter the holdermount 1210, the gap, G₁, will nominally be at least 0.05 mm and likelymore as a result of the doming 288.

In one embodiment, a spring clamping assembly is employed to allow theclamped foil portion to move in a radial direction. While a variety ofspring clamping assemblies are possible, in the depicted embodiment theholder mount 1210 is affixed to the bottom die 104 with a coil spring1481. The coil spring 1481 is compressed between the screw 1205 mountedto the bottom die 104 and the holder mount 1210 (or embossing foilholder 1201 since the holder is rigidly attached to the mount 1210). Thescrew 1205 may be adjusted to set tensioning of the foil holder 1201 toachieve a predetermined clamping force of the bottom embossing foil 251against the bottom die 104 (e.g., the bottom press pad 280). With thefoil holder 1201 a rigid extension of the holder mount 1210, theclamping force is substantially parallel to the longitudinal mandrelaxis 229. The clamping force is dependent on a number of factors, suchas the friction coefficients of the embossing foil 251, the foil holdermount 1210 and the bottom press pad 280. For exemplary embodiments, theclamping force ranges between approximately 5 N and 30 N.

Each of the screws 1205 depicted in FIG. 12A may be mounted with thecoil spring 1481 in the manner depicted in FIG. 14A to provide aplurality of coil springs spaced apart by an angular distance to providethe predetermined embossing foil clamping force. In an exemplaryembodiment, the 6 screws 1205 depicted in FIG. 12A are each mounted withthe coil spring 1481 to provide a total clamping force between 10 and 20N.

FIG. 14B illustrates a cross-sectional view of the single-sidedembossing foil holder of FIG. 14A when a press system is in a closedposition, in accordance with an embodiment. As shown, the recordingmedia disk substrate 255 is now against the bottom embossing foil 251and the bottom embossing foil 251 is expanded radially relative to thefoil holder 1201 and the holder mount 1210 so that the gap G₁ is reducedto the gap G₂.

Double-side imprinting embodiments may also provide a clamping forcewhich allows an outer circumference of an embossing foil to expandradially. For example, the assembly 1300, as depicted in FIGS. 13A-13Eis readily adapted to allow radial foil expansion by mounting the topand bottom holder mounts with a spring tensioning assembly in a mannersimilar to that described for a single-sided press system. As oneexemplary embodiment, each of the holder tabs 1302 may be mounted to thetop holder mount 1350 with coil springs 1481 to provide a predeterminedclamping force which allows the outer circumference of the top embossingfoil 150 to slide against the top die 102 towards the holder tabs 1302and top holder mount 1350. Each of the holder tabs 1325 may be mountedto the bottom holder mount 1310 with coil springs 1481 to provide apredetermined clamping force.

Whether employed in a double-sided configuration or a single-sidedconfiguration, the spring tensioned foil holders described herein may beutilized to press a recording media disk. For example, FIG. 3D depicts apressing method 375 which begins with clamping the embossing foil to aleast a first die using a spring tensioned clamp (e.g., employing coilsprings 1481) at operation 376. Next, at operation 377, a magneticrecording disk is received in a die press. At operation 378, the foil ispressed against the magnetic recording disk to form a discrete trackrecording pattern and the foil is allowed to expand by the springtensioned clamp. The die press is then unloaded at operation 379.

The above embodiments have been described with exemplary reference to a“magnetic recording disk” substrate only for consistency of discussion.It should be noted that other types and shapes of substrates may be used(e.g., wafer and panel oxide/substrates) having an embossable materialdisposed thereon. The apparatus and methods discussed herein may also beused in applications such as the production of semiconductor devices andliquid crystal display panels.

In an alternative embodiment, for example, the nano-imprinting presssystems and imprinting methods discussed herein may be used to fabricatepixel arrays for flat panel displays. In such a fabrication, anembossable material may be disposed above a base structure of, forexample, an indium tin oxide (ITO) layer on top of a substrate. Asanother example, the nano-imprinting apparatus and methods discussedherein may be used to fabricate lasers. In such a fabrication,embossable material areas patterned by the embossing foils are used as amask to define laser cavities for light emitting materials. In stillother embodiments, the apparatus and methods discussed herein may beused in other applications, for example, the production of multiplelayer electronic packaging, the production of optical communicationdevices, and contact/transfer printing.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary features thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader spirit and scope of theinvention as set forth in the appended claims. The specification andfigures are, accordingly, to be regarded in an illustrative rather thana restrictive sense.

What is claimed is:
 1. An imprinting method, comprising: clamping, with a spring tensioned clamp, a first portion of an embossing foil to a first die of a die press; receiving a magnetic recording disk in the die press; and pressing the embossing foil against the magnetic recording disk to emboss a side of the magnetic recording disk with a discrete track recording pattern, wherein the pressing is performed after the clamping of the first portion of the embossing foil to the first die.
 2. The method as in claim 1, further comprising allowing an outer perimeter edge of the embossing foil to slide in a radial direction between a surface of the spring tensioned clamp and a first surface of the first die.
 3. The method as in claim 1, further comprising rigidly affixing a second portion of the embossing foil to a mandrel sleeve surrounding a rod portion of a mandrel, the rod portion receiving the magnetic recording disk.
 4. The method as in claim 3, wherein the embossing foil has an annular shape, the clamped portion of the foil comprises at least a portion of the outer perimeter of the foil, and wherein the rigidly affixed second portion of the foil comprises at least a portion of an inner perimeter of the embossing foil. 